[Federal Register Volume 72, Number 68 (Tuesday, April 10, 2007)]
[Notices]
[Pages 17849-17864]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: E7-6750]


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DEPARTMENT OF COMMERCE

National Oceanic and Atmospheric Administration

[I.D. 040307B]


Small Takes of Marine Mammals Incidental to Specified Activities; 
Low-Energy Marine Seismic Survey in the Northeastern Indian Ocean, May-
August 2007

AGENCY:  National Marine Fisheries Service (NMFS), National Oceanic and 
Atmospheric Administration (NOAA), Commerce.

ACTION:  Notice; proposed incidental take authorization; request for 
comments.

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SUMMARY:  NMFS has received an application from Scripps Institute of 
Oceanography (SIO) for an Incidental Harassment Authorization (IHA) to 
take marine mammals incidental to conducting a low-energy marine 
seismic survey in the northeastern Indian Ocean during May-August 2007. 
Pursuant to the Marine Mammal Protection Act (MMPA), NMFS is requesting 
comments on its proposal to issue an IHA to SIO to incidentally take, 
by Level B harassment only, several species of marine mammals during 
the aforementioned activity.

DATES:  Comments and information must be received no later than May 10, 
2007.

ADDRESSES:  Comments on the application should be addressed to Michael 
Payne, Chief, Permits, Conservation and Education Division, Office of 
Protected Resources, National Marine Fisheries Service, 1315 East-West 
Highway, Silver Spring, MD 20910-3225. The mailbox address for 
providing email comments is <a href="/cdn-cgi/l/email-protection#326260031c02060201020570725c5d53531c555d44"><span class="__cf_email__" data-cfemail="09595b3827393d393a393e4b4967666868276e667f">[email protected]</span></a>. NMFS is not 
responsible for e-mail comments sent to addresses other than the one 
provided here. Comments sent via e-mail, including all attachments, 
must not exceed a 10-megabyte file size.
    A copy of the application containing a list of the references used 
in this document may be obtained by writing to the address specified 
above, telephoning the contact listed below (see FOR FURTHER 
INFORMATION CONTACT), or visiting the internet at: http://www.nmfs.noaa.gov/pr/permits/incidental.htm#applications.
    Documents cited in this notice may be viewed, by appointment, 
during regular business hours, at the aforementioned address.

FOR FURTHER INFORMATION CONTACT:  Jolie Harrison, Office of Protected 
Resources, NMFS, (301) 713-2289, ext 166.

SUPPLEMENTARY INFORMATION:

Background

    Sections 101(a)(5)(A) and (D) of the MMPA (16 U.S.C. 1361 et seq.) 
direct the Secretary of Commerce to allow, upon request, the 
incidental, but not intentional, taking of marine mammals by U.S. 
citizens who engage in a specified activity (other than commercial 
fishing) within a specified geographical region if certain findings are 
made and either regulations are issued or, if the taking is limited to 
harassment, a notice of a proposed authorization is provided to the 
public for review.
    Authorization shall be granted if NMFS finds that the taking will 
have a negligible impact on the species or stock(s), will not have an 
unmitigable adverse impact on the availability of the species or 
stock(s) for subsistence uses (where relevant), and if the permissible 
methods of taking and requirements pertaining to the mitigation, 
monitoring and reporting of such takings are set forth. NMFS has 
defined ``negligible impact'' in 50 CFR 216.103 as ''...an impact 
resulting from the specified activity that cannot be reasonably 
expected to, and is not reasonably likely to, adversely affect the 
species or stock through effects on annual rates of recruitment or 
survival.''
    Section 101(a)(5)(D) of the MMPA established an expedited process 
by which citizens of the United States can apply for an authorization 
to incidentally take small numbers of marine mammals by harassment. 
Except with respect to certain activities not pertinent here, the MMPA 
defines ``harassment'' as:
    any act of pursuit, torment, or annoyance which (i) has the 
potential to injure a marine mammal or marine mammal stock in the 
wild [Level A harassment]; or (ii) has the potential to disturb a 
marine mammal or marine mammal stock in the wild by causing 
disruption of behavioral patterns, including, but not limited to, 
migration, breathing, nursing, breeding, feeding, or sheltering 
[Level B harassment].
    Section 101(a)(5)(D) establishes a 45-day time limit for NMFS 
review of an application followed by a 30-day public notice and comment 
period on any proposed authorizations for the incidental harassment of 
marine mammals. Within 45 days of the close of the comment period, NMFS 
must either approve or deny the authorization.

Summary of Request

    On January 5, 2007, NMFS received an application from SIO for the 
taking, by Level B harassment only, of 32 species of marine mammals 
incidental to conducting, with research funding from the National 
Science Foundation (NSF), a low-energy marine seismic survey in the 
northeastern Indian Ocean from May-August 2007. The purpose of the 
research program is to conduct a scientific rock-dredging, magnetic, 
bathymetric, and seismic survey program at nine sites on the Ninety 
East Ridge in the northeastern Indian Ocean. The results will be used 
to (1) determine the morphology, structure, and tectonics of ridge 
volcanoes to see whether they reflect centralized (plume) or 
distributed (crack) eruptions; (2) infer the magmatic evolution of the 
ridge, whether it fits the plume hypothesis, and its connection to 
existing hotspots; (3) examine the duration of volcanism at the various 
sites and along the ridge to see whether the age progression fits the 
simple plume model; and (4) survey broad characteristics of subseafloor 
in

[[Page 17850]]

order to refine the planning of the IODP drilling proposal. Included in 
the research planned for 2007 are scientific rock dredging at all nine 
sites, high-resolution seismic methods to image the subsea floor at 
five of the sites, and the use of a magnetometer, gravimeter, multi-
beam sonar, and sub-bottom profiler throughout the cruise.

Description of the Activity

    The seismic surveys will involve one vessel, the R/V Roger Revelle 
(Roger Revelle), which is scheduled to depart from Fremantle, 
Australia, between May 22 and June 19, 2007. The Roger Revelle will 
conduct the cruise in the Indian Ocean and arrive at Colombo, Sri 
Lanka, between July 16 and August 13, 2007. The exact dates of the 
activities may vary by a few days because of weather conditions, 
repositioning, streamer operations and adjustments, airgun deployment, 
or the need to repeat some lines if data quality is substandard. 
Additional seismic operations may be occasionally needed to investigate 
significant new findings as revealed by the other survey systems. The 
overall area within which the seismic surveys will occur is located 
between approximately 5[deg] N. and 25[deg] S., along approximately 90o 
E. (Figure 1 in the application), in the Indian Ocean. The surveys will 
be conducted entirely in International Waters.
    The Roger Revelle will deploy a pair of low-energy Generator-
Injector (GI) airguns as an energy source (each with a discharge volume 
of 45 in\3\), plus a 800 m-long (2625-ft long), 48-channel, towed 
hydrophone. The program will consist of approximately 2700 km (1678 mi) 
of surveys, including turns. Water depths within the seismic survey 
areas are 1600-5100 m (1750-5577 yd). The GI guns will be operated on a 
small grid for approximately 49 hours at each of 5 sites over a 
approximately 50-day period during May-August 2007, commencing between 
May 22 and June 19. There will be additional seismic operations 
associated with equipment testing, start-up, and repeat coverage of any 
areas where initial data quality is sub-standard.
    In addition to the operations of the GI guns, a 3.5-kHz sub-bottom 
profiler , a Kongsberg-Simrad EM-120 multi-beam sonar, and a gravimeter 
will be used continuously throughout the cruise, and passive 
geophysical sensors will be deployed to conduct magnetic surveys at all 
times except during dredging.

Vessel Specifications

    The Roger Revelle has a length of 83 m (272 ft), a beam of 16 m (52 
ft), and a maximum draft of 5.2 m. The ship is powered by two 3,000 hp 
Propulsion General Electric motors and an 1180-hp Azimuthing jet bow 
thruster. An operation speed of 11.1 km/h (6 knots) is used during 
seismic acquisition. When not towing seismic survey gear, the Roger 
Revelle cruises at 22.2-23.1 km/h (12-12.5 knots) and has a maximum 
speed of 27.8 km/h (15 knots). It has a normal operating range of 
approximately 27,780 km (17,262 mi).

Acoustic Source Specifications

Seismic Airguns
    The vessel Roger Revelle will tow a pair of GI airguns and an 800 
m-long (2624-ft), 48-channel hydrophone streamer. Seismic pulses will 
be emitted at intervals of 6-10 seconds, which corresponds to a shot 
interval of approximatley 18.5-31 m (61-102 ft) (at a speed of 6 knots 
(11.1 km/h). The generator chamber of each GI gun, the one responsible 
for introducing the sound pulse into the ocean, is 45 in\3\ (total air 
discharge approximately 90 in\3\). The larger (105 in\3\) injector 
chamber injects air into the previously-generated bubble to maintain 
its shape, and does not introduce more sound into the water. The two 45 
in\3\ GI guns will be towed 8 m (26 ft) apart side by side, 21 m (69 
ft) behind the Roger Revelle, at a depth of 2 m (6.6 ft). The dominant 
frequency components are 0-188 Hz.
    The sound pressure field of that GI gun variation has not been 
modeled, but that for two 45 in\3\ Nucleus G guns (which actually have 
more energy than GI guns of the same size) has been modeled by the 
Lamont-Doherty Earth Observatory (L-DEO) in relation to distance and 
direction from the airguns. This source, which is directed downward, 
was found to have an output (0-peak) of 230.6 dB re 1 microPa m. The 
nominal downward-directed source levels indicated above do not 
represent actual sound levels that can be measured at any location in 
the water. Rather, they represent the level that would be found 1 m 
from a hypothetical point source emitting the same total amount of 
sound as is emitted by the combined GI guns. The actual received level 
at any location in the water near the GI guns will not exceed the 
source level of the strongest individual source. In this case, that 
will be about 224.6 dB re 1 microPa-m peak, or 229.8 dB re 1 microPa-m 
peak-to-peak. Actual levels experienced by any organism more than 1 m 
from either GI gun will be significantly lower.
    A further consideration is that the rms (root mean square) received 
levels that are used as impact criteria for marine mammals are not 
directly comparable to the peak or peak to peak values normally used to 
characterize source levels of airgun arrays. The measurement units used 
to describe airgun sources, peak or peak-to-peak decibels, are always 
higher than the ``root mean square'' (rms) decibels referred to in 
biological literature. A measured received level of 160 dB rms in the 
far field would typically correspond to a peak measurement of 
approximately 170 to 172 dB, and to a peak-to-peak measurement of 
approximately 176 to 178 dB, as measured for the same pulse received at 
the same location (Greene 1997; McCauley et al., 1998, 2000). The 
precise difference between rms and peak or peak-to-peak values depends 
on the frequency content and duration of the pulse, among other 
factors. However, the rms level is always lower than the peak or peak-
to-peak level for an airgun-type source.
Bathymetric Sonar
    The Roger Revelle will utilize the Kongsberg-Simrad EM120 multi-
beam sonar, which operates at 11.25-12.6 kHz and is mounted in the 
hull. It operates in several modes, depending on water depth. In the 
proposed survey, it will be used in deep (>800-m (2625 ft)) water, and 
will operate in ``Deep'' mode. The beam width is 1[deg] or 2[deg] fore-
aft and a total of 150[deg] athwartship. Estimated maximum source 
levels are 239 and 233 dB at 1[deg] and 2[deg] beam widths, 
respectively. Each ``ping'' consists of nine successive fan-shaped 
transmissions, each ensonifying a sector that extends 1[deg] or 2[deg] 
fore-aft. In the ``Deep'' mode, the total duration of the transmission 
into each sector is 15 ms. The nine successive transmissions span an 
overall cross-track angular extent of about 150 degrees, with 16 ms 
gaps between the pulses for successive sectors. A receiver in the 
overlap area between two sectors would receive two 15-ms pulses 
separated by a 16-ms gap. The ``ping'' interval varies with water 
depth, from approximately 5 s at 1000 m (3280 ft) to 20 s at 4000 m 
(13120 ft).
Sub-bottom Profiler
    The Roger Revelle will utilize the Knudsen Engineering Model 320BR 
sub-bottom profiler, which is a dual-frequency transceiver designed to 
operate at 3.5 and/or 12 kHz. It is used in conjunction with the multi-
beam sonar to provide data about the sedimentary features that occur 
below the sea floor. The energy from the sub-bottom profiler is 
directed downward (in an 80-degree cone) via a 3.5-kHz transducer array 
mounted in the hull. The maximum power output of the

[[Page 17851]]

320BR is 10 kilowatts for the 3.5-kHz section and 2 kilowatts for the 
12-kHz section. (The 12-kHz section is seldom used in survey mode on 
Roger Revelle because of overlap with the operating frequency of the 
Kongsberg Simrad EM-120 multi-beam sonar.)
    The pulse length for the 3.5 kHz section of the 320BR is 0.8-24 ms, 
controlled by the system operator in regards to water depth and 
reflectivity of the bottom sediments, and will usually be 12 or 24 ms 
in this survey. The system produces one sound pulse and then waits for 
its return before transmitting again. Thus, the pulse interval is 
directly dependent upon water depth, and in this survey is 4.5-8 sec. 
Using the Sonar Equations and assuming 100 percent efficiency in the 
system (impractical in real world applications), the source level for 
the 320BR is calculated to be 211 dB re 1 microPa-m. In practice, the 
system is rarely operated above 80 percent power level.

Safety Radii

    NMFS has determined that for acoustic effects, using acoustic 
thresholds in combination with corresponding safety radii is the most 
effective way to consistently apply measures to avoid or minimize the 
impacts of an action, and to quantitatively estimate the effects of an 
action. Thresholds are used in two ways: (1) to establish a mitigation 
shut-down or power down zone, i.e., if an animal enters an area 
calculated to be ensonified above the level of an established 
threshold, a sound source is powered down or shut down; and (2) to 
calculate take, in that a model may be used to calculate the area 
around the sound source that will be ensonified to that level or above, 
then, based on the estimated density of animals and the distance that 
the sound source moves, NMFS can estimate the number of marine mammals 
that may be ``taken''. NMFS believes that to avoid permanent 
physiological damage (Level A Harassment), cetaceans and pinnipeds 
should not be exposed to pulsed underwater noise at received levels 
exceeding, respectively, 180 and 190 dB re 1 microPa (rms). NMFS also 
assumes that cetaceans or pinnipeds exposed to levels exceeding 160 dB 
re 1 microPa (rms) may experience Level B Harassment.
    Received sound levels have been modeled by L-DEO for a number of 
airgun configurations, including two 45-in\3\ Nucleus G-guns, in 
relation to distance and direction from the airguns. The model does not 
allow for bottom interactions, and is most directly applicable to deep 
water. Based on the modeling, estimates of the maximum distances from 
the GI guns where sound levels of 190, 180, and 160 dB re 1 microPa 
(rms) are predicted to be received in deep (>1000-m (3280-ft)) water 
are 10, 40, and 400 m (33, 131, and 1312 ft), respectively. Because the 
model results are for G guns, which have more energy than GI guns of 
the same size, those distances are overestimates of the distances for 
the 45-in\3\ GI guns.
    Empirical data concerning the 180- and 160- dB distances have been 
acquired based on measurements during the acoustic verification study 
conducted by L-DEO in the northern Gulf of Mexico from 27 May to 3 June 
2003 (Tolstoy et al., 2004). Although the results are limited, the data 
showed that radii around the airguns where the received level would be 
180 dB re 1 microPa (rms) vary with water depth. Similar depth-related 
variation is likely in the 190-dB distances applicable to pinnipeds. 
Correction factors were developed for water depths 100-1000 m (328-3280 
ft) and <100 m (328 ft). The proposed survey will occur in depths 1600-
5100 m (5249-16732 ft), so the correction factors are not relevant 
here.
    The empirical data indicate that, for deep water (>1000 m (3280 
ft)), the L-DEO model tends to overestimate the received sound levels 
at a given distance (Tolstoy et al., 2004). However, to be 
precautionary pending acquisition of additional empirical data, it is 
proposed that safety radii during airgun operations in deep water will 
be the values predicted by L-DEO's model (above). Therefore, the 
assumed 180- and 190-dB radii are 40 m and 10 m (131 and 33 ft), 
respectively.
    Airguns will be shut down immediately when cetaceans or pinnipeds 
are detected within or about to enter the appropriate 180-dB (rms) or 
190-dB (rms) radius, respectively.

Description of Marine Mammals in the Activity Area

    Thirty-two species of cetacean, including 25 odontocete (dolphins 
and small and large toothed whales) species and seven mysticete (baleen 
whales) species, are thought to occur in the proposed seismic survey 
areas along the Ninety East Ridge in the northeastern Indian Ocean 
(Table 1). Several are listed under the U.S. Endangered Species Act 
(ESA) as Endangered: the sperm whale, humpback whale, blue whale, fin 
whale, and sei whale.
    Although there have been several surveys of marine mammals in the 
Indian Ocean (e.g., Keller et al., 1982; Leatherwood et al., 1984; Eyre 
1995; Baldwin et al., 1998; de Boer 2000; de Boer et al., 2003), data 
on the occurrence, distribution, and abundance of odontocetes and 
mysticetes in the northeastern Indian Ocean, encompassing the proposed 
seismic survey area along the Ninety East Ridge, are limited or 
lacking. Commercial whaling severely depleted all the large whale 
populations in this region, and subsequently, in 1979, the 
International Whaling Commission declared the Indian Ocean north of 
55[deg] S. latitude a whale sanctuary. The majority of recent detailed 
information on whales within the Indian Ocean Sanctuary (IOS) comes 
from
    (1) A United Nations Environment Programme (UNEP) Report 
summarizing cetacean research in the western IOS (Leatherwood and 
Donovan 1991);
    (2) A compilation of sightings for the entire IOS produced by the 
Whale and Dolphin Conservation Society (de Boer et al., 2003); and
    (3) A review of marine mammals records in India (Sathasivam 2004); 
and
    (4) A series of research cruises within the IOS (Keller et al., 
1982; Leatherwood et al., 1984; Corbett 1994; Eyre 1995; Ballance and 
Pitman 1998; de Boer 2000).
    Because the proposed survey area spans such a wide range of 
latitudes (approximately 5[deg] N.-25[deg] S.), tropical and temperate 
species are found there. The survey area is all in deep-water habitat 
but is close to oceanic island habitats (i.e., Andaman, Nicobar, and 
Cocos (Keeling) Islands), so both coastal and oceanic species might be 
encountered, although species that stay in very shallow water (e.g., 
Indian hump-backed dolphin, Irrawaddy dolphin, and finless porpoise) 
would not. Abundance and density estimates of cetaceans found in areas 
other than the northeastern and central Indian Ocean are provided for 
reference only, and are not necessarily the same as those in the survey 
area. Table 1 also shows the estimated abundance of the marine mammals 
likely to be encountered during the Roger Revelle's cruise. Additional 
information regarding the distribution of these species and how the 
estimated densities were calculated may be found in SIO's application.

[[Page 17852]]



----------------------------------------------------------------------------------------------------------------
                Species                          Habitat                 Occurrence              Rqstd Take
----------------------------------------------------------------------------------------------------------------
Mysticetes
 
Humpback whale (Megaptera               Mainly nearshore waters    Common                  5(0)**
 novaeangliae)*                          and banks
----------------------------------------------------------------------------------------------------------------
Minke whale (Balaenoptera               Pelagic and coastal        Uncommon                5
 acutorostrata)
----------------------------------------------------------------------------------------------------------------
Antarctic minke whale (Balaenoptera     Coastal and oceanic        Uncommon                5
 bonaerensis)
----------------------------------------------------------------------------------------------------------------
Bryde's whale (Balaenoptera edeni)      Pelagic and coastal        Very common             5
----------------------------------------------------------------------------------------------------------------
Sei whale (Balaenoptera borealis) *     Primarily offshore,        Uncommon                5(0)**
                                         pelagic
----------------------------------------------------------------------------------------------------------------
Fin whale (Balaenoptera physalus)*      Continental slope, mostly  Common                  5(0)**
                                         pelagic
----------------------------------------------------------------------------------------------------------------
Blue whale (Balaenoptera musculus)*     Pelagic and coastal        Very common             5(1)**
----------------------------------------------------------------------------------------------------------------
Odontocetes
 
Sperm whale (Physeter macrocephalus)*   Usually pelagic and deep   Common                  5(1)**
                                         seas
----------------------------------------------------------------------------------------------------------------
Pygmy sperm whale (Kogia breviceps)     Deep waters off the shelf  Common                  5
----------------------------------------------------------------------------------------------------------------
Dwarf sperm whale (Kogia sima)          Deep waters off the shelf  Common                  5
----------------------------------------------------------------------------------------------------------------
Cuvier's beaked whale (Ziphius          Pelagic                    Common                  5
 cavirostris)
----------------------------------------------------------------------------------------------------------------
Shepherd's beaked whale (Tasmacetus     Pelagic                    Rare                    5
 shepherdi))
----------------------------------------------------------------------------------------------------------------
Longman's beaked whale (Indopacetus     Pelagic                    Common?                 1
 pacificus)
----------------------------------------------------------------------------------------------------------------
Southern bottlenose whale (Hyperoodon   Pelagic                    Uncommon                5
 planifrons)
----------------------------------------------------------------------------------------------------------------
True's beaked whale (Mesoplodon mirus)  Pelagic                    Rare                    5
----------------------------------------------------------------------------------------------------------------
Gray's beaked whale (Mesoplodon grayi)  Pelagic                    Uncommon                5
----------------------------------------------------------------------------------------------------------------
Ginkgo-toothed whale (Mesoplodon        Pelagic                    Common                  5
 ginkgodens)
----------------------------------------------------------------------------------------------------------------
Blainville's beaked whale (Mesoplodon   Pelagic                    Very common             5
 densirostris)
----------------------------------------------------------------------------------------------------------------
Rough-toothed dolphin (Steno            Deep water                 Uncommon                69
 bredanensis)
----------------------------------------------------------------------------------------------------------------
Bottlenose dolphin (Tursiops            Coastal and oceanic,       Common                  129
 truncatus)                              shelf break
----------------------------------------------------------------------------------------------------------------
Pantropical spotted dolphin (Stenella   Coastal and pelagic        Uncommon                65
 attenuata)
----------------------------------------------------------------------------------------------------------------
Spinner dolphin (Stenella               Coastal and pelagic        Abundant                215
 longirostris)
----------------------------------------------------------------------------------------------------------------
Striped dolphin (Stenella               Off continental shelf      Common                  86
 coeruleoalba)
----------------------------------------------------------------------------------------------------------------
Fraser's dolphin (Lagenodelphis hosei)  Waters >1000 m             Rare                    22
----------------------------------------------------------------------------------------------------------------
Common dolphin (Delphinus delphis)      Shelf and pelagic,         Very common             151
                                         seamounts
----------------------------------------------------------------------------------------------------------------
Risso's dolphin (Grampus griseus)       Waters >1000 m, seamounts  Very common             151
----------------------------------------------------------------------------------------------------------------
Melon-headed whale (Peponocephala       Oceanic                    Very common             50
 electra)
----------------------------------------------------------------------------------------------------------------
Pygmy killer whale (Feresa attenuata)   Deep, pantropical waters   Common                  25
----------------------------------------------------------------------------------------------------------------
False killer whale (Pseudorca           Pelagic                    Common                  15
 crassidens)
----------------------------------------------------------------------------------------------------------------
Killer whale (Orcinus orca)             Widely distributed         Common                  5
----------------------------------------------------------------------------------------------------------------
Long-finned pilot whale (Globicephala   Mostly pelagic             Rare                    30
 melas)
----------------------------------------------------------------------------------------------------------------

[[Page 17853]]

 
Short-finned pilot whale (Globicephala  Mostly pelagic, high-      Very common             15
 macrorhynchus)                          relief topography
----------------------------------------------------------------------------------------------------------------
Table 1. Species expected to be encountered (and potentially harassed) during SIO's Indian Ocean cruise
*Species are listed as endangered under the Endangered Species Act
**Parenthetical numbers represent numbers of takes NMFS proposes to authorize (we may not authorize take
  ofspecies, or take of numbers of species, that we are not exempted pursuant to our internal ESA consultation)

Potential Effects on Marine Mammals

Potential Effects of Airguns

    The effects of sounds from airguns might include one or more of the 
following: tolerance, masking of natural sounds, behavioral 
disturbance, and temporary or permanent hearing impairment (Richardson 
et al., 1995). Given the small size of the GI guns planned for the 
present project, effects are anticipated to be considerably less than 
would be the case with a large array of airguns. It is very unlikely 
that there would be any cases of temporary or, especially, permanent 
hearing impairment. Also, behavioral disturbance is expected to be 
limited to relatively short distances.
Tolerance
    Numerous studies have shown that pulsed sounds from airguns are 
often readily detectable in the water at distances of many kilometers. 
For a summary of the characteristics of airgun pulses, see Appendix A 
of SIO's application. However, it should be noted that most of the 
measurements of airgun sounds that have been reported concerned sounds 
from larger arrays of airguns, whose sounds would be detectable 
considerably farther away than the GI guns planned for use in the 
present project.
    Numerous studies have shown that marine mammals at distances more 
than a few kilometers from operating seismic vessels often show no 
apparent response-see Appendix A (e) of SIO's application. That is 
often true even in cases when the pulsed sounds must be readily audible 
to the animals based on measured received levels and the hearing 
sensitivity of that mammal group. Although various baleen whales, 
toothed whales, and (less frequently) pinnipeds have been shown to 
react behaviorally to airgun pulses under some conditions, at other 
times mammals of all three types have shown no overt reactions. In 
general, pinnipeds and small odontocetes seem to be more tolerant of 
exposure to airgun pulses than are baleen whales. Given the relatively 
small and low-energy airgun source planned for use in this project, 
mammals (and sea turtles) are expected to tolerate being closer to this 
source than might be the case for a larger airgun source typical of 
most seismic surveys.
Masking
    Masking effects of pulsed sounds (even from large arrays of 
airguns) on marine mammal calls and other natural sounds are expected 
to be limited, although there are very few specific data on this. Some 
whales are known to continue calling in the presence of seismic pulses. 
Their calls can be heard between the seismic pulses (e.g., Richardson 
et al., 1986; McDonald et al., 1995; Greene et al., 1999; Nieukirk et 
al., 2004). Although there has been one report that sperm whales cease 
calling when exposed to pulses from a very distant seismic ship (Bowles 
et al., 1994), a recent study reports that sperm whales off northern 
Norway continued calling in the presence of seismic pulses (Madsen et 
al., 2002c). That has also been shown during recent work in the Gulf of 
Mexico (Tyack et al., 2003). Given the small source planned for use 
here, there is even less potential for masking of baleen or sperm whale 
calls during the present study than in most seismic surveys. Masking 
effects of seismic pulses are expected to be negligible in the case of 
the smaller odontocete cetaceans, given the intermittent nature of 
seismic pulses and the relatively low source level of the airguns to be 
used here. Also, the sounds important to small odontocetes are 
predominantly at much higher frequencies than are airgun sounds. 
Masking effects, in general, are discussed further in Appendix A (d) of 
SIO's application.
Disturbance Reactions
    Disturbance includes a variety of effects, including subtle changes 
in behavior, more conspicuous changes in activities, and displacement. 
Disturbance is one of the main concerns in this project. Reactions to 
sound, if any, depend on species, state of maturity, experience, 
current activity, reproductive state, time of day, and many other 
factors. If a marine mammal responds to an underwater sound by changing 
its behavior or moving a small distance, the response may or may not 
rise to the level of harassment, let alone affect the stock or the 
species as a whole. Alternatively, if a sound source displaces marine 
mammals from an important feeding or breeding area, effects on the 
stock or species could potentially be more than negligible. Given the 
many uncertainties in predicting the quantity and types of impacts of 
noise on marine mammals, it is common practice to estimate how many 
mammals are likely to be present within a particular distance of 
industrial activities, or exposed to a particular level of industrial 
sound. This practice potentially overestimates the numbers of marine 
mammals that are affected in some biologically important manner.
    The sound criteria used to estimate how many marine mammals might 
be disturbed to some biologically-important degree by a seismic program 
are based on behavioral observations during studies of several species. 
However, information is lacking for many species. Detailed studies have 
been done on humpback, gray, and bowhead whales, and on ringed seals. 
Less detailed data are available for some other species of baleen 
whales, sperm whales, and small toothed whales. Most of those studies 
have focused on the impacts resulting from the use of much larger 
airgun sources than those planned for use in the present project. Thus, 
effects are expected to be limited to considerably smaller distances 
and shorter periods of exposure in the present project than in most of 
the previous work concerning marine mammal reactions to airguns.
    Baleen Whales - Baleen whales generally tend to avoid operating 
airguns, but avoidance radii are quite variable. Whales are often 
reported to show no overt reactions to pulses from large arrays of 
airguns at distances beyond a few kilometers, even though the airgun 
pulses remain well above ambient noise levels out to much longer 
distances. However, as reviewed in Appendix A (e) of SIO's application, 
baleen whales exposed to strong noise pulses from airguns often react 
by deviating from their normal migration route and/or interrupting 
their feeding activities and moving away from the sound source. In the 
case of the migrating gray and bowhead whales, the observed changes in 
behavior appeared

[[Page 17854]]

to be of little or no biological consequence to the animals. They 
simply avoided the sound source by displacing their migration route to 
varying degrees, but within the natural boundaries of the migration 
corridors.
    Studies of gray, bowhead, and humpback whales have determined that 
received levels of pulses in the 160-170 dB re 1 microPa rms range seem 
to cause obvious avoidance behavior in a substantial fraction of the 
animals exposed. In many areas, seismic pulses from large arrays of 
airguns diminish to those levels at distances ranging from 4.5-14.5 km 
(2.8-9 mi) from the source. A substantial proportion of the baleen 
whales within those distances may show avoidance or other strong 
disturbance reactions to the airgun array. Subtle behavioral changes 
sometimes become evident at somewhat lower received levels, and recent 
studies, reviewed in Appendix A (e) of SIO's application, have shown 
that some species of baleen whales, notably bowheads and humpbacks, at 
times show strong avoidance at received levels lower than 160-170 dB re 
1 microPa rms. Reaction distances would be considerably smaller during 
the present project, in which the 160-dB radius is predicted to be 
approximately 0.40 km (0.9 mi), as compared with several kilometers 
when a large array of airguns is operating.
    Humpback whales summering in southeast Alaska did not exhibit 
persistent avoidance when exposed to seismic pulses from a 1.64-L (100 
in\3\) airgun (Malme et al., 1985). Some humpbacks seemed ``startled'' 
at received levels of 150-169 dB re 1 microPa on an approximate rms 
basis. Malme et al. (1985) concluded that there was no clear evidence 
of avoidance, despite the possibility of subtle effects, at received 
levels up to 172 re 1 microPa (approximately rms). More detailed 
information on responses of humpback whales to seismic pulses during 
studies in Australia can be found in Appendix A (a) of SIO's 
application.
    Malme et al. (1986, 1988) studied the responses of feeding eastern 
gray whales to pulses from a single 100 in3 airgun off St. Lawrence 
Island in the northern Bering Sea. They estimated, based on small 
sample sizes, that 50 percent of feeding gray whales ceased feeding at 
an average received pressure level of 173 dB re 1 microPa on an 
(approximate) rms basis, and that 10 percent of feeding whales 
interrupted feeding at received levels of 163 dB. Those findings were 
generally consistent with the results of experiments conducted on 
larger numbers of gray whales that were migrating along the California 
coast.
    Data on short-term reactions (or lack of reactions) of cetaceans to 
impulsive noises do not necessarily provide information about long-term 
effects. It is not known whether impulsive noises affect reproductive 
rate or distribution and habitat use in subsequent days or years. 
However, gray whales continued to migrate annually along the west coast 
of North America despite intermittent seismic exploration and much ship 
traffic in that area for decades (Appendix A in Malme et al., 1984). 
Bowhead whales continued to travel to the eastern Beaufort Sea each 
summer despite seismic exploration in their summer and autumn range for 
many years (Richardson et al., 1987). In any event, the brief exposures 
to sound pulses from the present small airgun source are highly 
unlikely to result in prolonged effects.
    Toothed Whales - Little systematic information is available about 
reactions of toothed whales to noise pulses. Few studies similar to the 
more extensive baleen whale/seismic pulse work summarized above have 
been reported for toothed whales. However, systematic work on sperm 
whales is underway (Tyack et al., 2003).
    Seismic operators sometimes see dolphins and other small toothed 
whales near operating airgun arrays, but in general there seems to be a 
tendency for most delphinids to show some limited avoidance of seismic 
vessels operating large airgun systems. However, some dolphins seem to 
be attracted to the seismic vessel and floats, and some ride the bow 
wave of the seismic vessel even when large arrays of airguns are 
firing. Nonetheless, there have been indications that small toothed 
whales sometimes tend to head away, or to maintain a somewhat greater 
distance from the vessel, when a large array of airguns is operating 
than when it is silent (e.g., Goold, 1996; Calambokidis and Osmek, 
1998; Stone, 2003). Similarly, captive bottlenose dolphins and beluga 
whales exhibit changes in behavior when exposed to strong pulsed sounds 
similar in duration to those typically used in seismic surveys 
(Finneran et al., 2000, 2002). However, the animals tolerated high 
received levels of sound (pk-pk level >200 dB re 1 microPa) before 
exhibiting aversive behaviors. With the presently-planned small airgun 
system, such levels would only be found within a few meters of the 
airguns.
    There are no specific data on the behavioral reactions of beaked 
whales to seismic surveys. A few beaked whale sightings have been 
reported from seismic vessels (Stone, 2003), however, based on limited 
observations most beaked whales tend to avoid approaching vessels of 
other types (e.g., Kasuya, 1986; Wursig et al., 1998). Several beaked 
whale strandings have been associated with naval mid-frequency sonar 
exercises, however, the sounds produced by seismic airguns are quite 
different from tactical sonar (see Appendix A (g) of SIO's 
application). The strandings mentioned above are apparently at least in 
part a disturbance response, although auditory or other injuries may 
also be a factor. Whether beaked whales would ever react similarly to 
seismic surveys is unknown (see ``Strandings and Mortality'', below).
    Sperm whales have been reported to show avoidance reactions to 
standard vessels not emitting airgun sounds, and it is to be expected 
that they would tend to avoid an operating seismic survey vessel. There 
were some limited early observations suggesting that sperm whales in 
the Southern Ocean and Gulf of Mexico might be fairly sensitive to 
airgun sounds from distant seismic surveys. However, more extensive 
data from recent studies in the North Atlantic suggest that sperm 
whales in those areas show little evidence of avoidance or behavioral 
disruption in the presence of operating seismic vessels (McCall Howard, 
1999; Madsen et al., 2002c; Stone, 2003).
    Odontocete reactions to large arrays of airguns are variable and, 
at least for small odontocetes, seem to be confined to a smaller radius 
than has been observed for mysticetes. Thus, behavioral reactions of 
odontocetes to the small airgun source to be used here are expected to 
be very localized, probably to distances <0.40 km (.25 mi).
    Pinnipeds - Pinnipeds are not likely to show a strong avoidance 
reaction to the small airgun source that will be used. Visual 
monitoring from seismic vessels, usually employing larger sources, has 
shown only slight (if any) avoidance of airguns by pinnipeds, and only 
slight (if any) changes in behavior-see Appendix A (e) of SIO's 
application. Those studies show that pinnipeds frequently do not avoid 
the area within a few hundred meters of operating airgun arrays, even 
for arrays much larger than the one to be used here (e.g., Harris et 
al., 2001). However, initial telemetry work suggests that avoidance and 
other behavioral reactions to small airgun sources may be stronger than 
evident to date from visual studies of pinniped reactions to airguns 
(Thompson et al., 1998). Even if reactions of the species occurring in 
the present study area are as strong as those evident in the telemetry 
study, reactions are expected to be confined to relatively

[[Page 17855]]

small distances and durations, with no long-term effects on pinnipeds.
    Additional details on the behavioral reactions (or the lack 
thereof) by all types of marine mammals to seismic vessels can be found 
in Appendix A (e) of SIO's application.
Hearing Impairment and Other Physical Effects
    Temporary or permanent hearing impairment is a possibility when 
marine mammals are exposed to very strong sounds, but there has been no 
specific documentation of this for marine mammals exposed to sequences 
of airgun pulses. Current NMFS policy regarding exposure of marine 
mammals to high-level sounds is that cetaceans and pinnipeds should not 
be exposed to impulsive sounds of 180 and 190 dB re 1 microPa (rms), 
respectively. Those criteria have been used in defining the safety 
(shut-down) radii planned for the proposed seismic survey. The 
precautionary nature of these criteria is discussed in Appendix A (f) 
of SIO's application, including the fact that the minimum sound level 
necessary to cause permanent hearing impairment is higher, by a 
variable and generally unknown amount, than the level that induces 
barely-detectable temporary threshold shift (TTS) (which NMFS' criteria 
are based on) and the level associated with the onset of TTS is often 
considered to be a level below which there is no danger of permanent 
damage. NMFS is presently developing new noise exposure criteria for 
marine mammals that take account of the now-available data on TTS in 
marine (and terrestrial) mammals.
    Because of the small size of the airgun source in this project (two 
45-in\3\ GI guns), along with the planned monitoring and mitigation 
measures, there is little likelihood that any marine mammals will be 
exposed to sounds sufficiently strong to cause hearing impairment. 
Several aspects of the planned monitoring and mitigation measures for 
this project are designed to detect marine mammals occurring near the 
two GI airguns (and multi-beam bathymetric sonar), and to avoid 
exposing them to sound pulses that might, at least in theory, cause 
hearing impairment. In addition, many cetaceans are likely to show some 
avoidance of the area with high received levels of airgun sound (see 
above). In those cases, the avoidance responses of the animals 
themselves will reduce or (most likely) avoid any possibility of 
hearing impairment.
    Non-auditory physical effects may also occur in marine mammals 
exposed to strong underwater pulsed sound. Possible types of non-
auditory physiological effects or injuries that theoretically might 
occur in mammals close to a strong sound source include stress, 
neurological effects, bubble formation, resonance effects, and other 
types of organ or tissue damage. It is possible that some marine mammal 
species (i.e., beaked whales) may be especially susceptible to injury 
and/or stranding when exposed to strong pulsed sounds. However, as 
discussed below, there is no definitive evidence that any of these 
effects occur even for marine mammals in close proximity to large 
arrays of airguns. It is especially unlikely that any effects of these 
types would occur during the present project given the small size of 
the source, the brief duration of exposure of any given mammal, and the 
planned monitoring and mitigation measures (see below). The following 
subsections discuss in somewhat more detail the possibilities of TTS, 
permanent threshold shift (PTS), and non-auditory physical effects.
    Temporary Threshold Shift (TTS) - TTS is the mildest form of 
hearing impairment that can occur during exposure to a strong sound 
(Kryter, 1985). While experiencing TTS, the hearing threshold rises and 
a sound must be stronger in order to be heard. TTS can last from 
minutes or hours to (in cases of strong TTS) days. For sound exposures 
at or somewhat above the TTS threshold, hearing sensitivity recovers 
rapidly after exposure to the noise ends. Only a few data on sound 
levels and durations necessary to elicit mild TTS have been obtained 
for marine mammals, and none of the published data concern TTS elicited 
by exposure to multiple pulses of sound.
    For toothed whales exposed to single short pulses, the TTS 
threshold appears to be, to a first approximation, a function of the 
energy content of the pulse (Finneran et al., 2002). Given the 
available data, the received level of a single seismic pulse might need 
to be approximately 210 dB re 1 microPa rms (approximately 221-226 dB 
pk-pk) in order to produce brief, mild TTS. Exposure to several seismic 
pulses at received levels near 200-205 dB (rms) might result in slight 
TTS in a small odontocete, assuming the TTS threshold is (to a first 
approximation) a function of the total received pulse energy. Seismic 
pulses with received levels of 200-205 dB or more are usually 
restricted to a radius of no more than 100 m (328 ft) around a seismic 
vessel operating a large array of airguns. Such levels would be limited 
to distances within a few meters of the small GI-gun source to be used 
in this project.
    For baleen whales, there are no data, direct or indirect, on levels 
or properties of sound that are required to induce TTS. However, no 
cases of TTS are expected given the small size of the source, and, as 
mentioned previously, there is a strong likelihood that baleen whales 
would avoid the approaching GI gun (or vessel), with the sound source 
operating, before being exposed to levels high enough for there to be 
any possibility of TTS.
    In pinnipeds, TTS thresholds associated with exposure to brief 
pulses (single or multiple) of underwater sound have not been measured. 
Initial evidence from prolonged exposures suggested that some pinnipeds 
may incur TTS at somewhat lower received levels than do small 
odontocetes exposed for similar durations (Kastak et al., 1999; Ketten 
et al., 2001; cf. Au et al., 2000). However, more recent indications 
are that TTS onset in the most sensitive pinniped species studied 
(harbor seal) may occur at a similar sound exposure level as in 
odontocetes (Kastak et al., 2004).
    A marine mammal within a radius of 100 m (328 ft) around a typical 
large array of operating airguns might be exposed to a few seismic 
pulses with levels of 205 dB, and possibly more pulses if the mammal 
moved with the seismic vessel. (As noted above, most cetacean species 
tend to avoid operating airguns, although not all individuals do so.) 
In addition, ramping up airgun arrays, which is standard operational 
protocol for large airgun arrays, provides an opportunity for cetaceans 
to move away from the seismic source and to avoid being exposed to the 
full acoustic output of the airgun array. However, several of the 
considerations that are relevant in assessing the impact of typical 
seismic surveys with arrays of airguns are not directly applicable 
here:
    (1) The planned GI gun source is much smaller, with correspondingly 
smaller radii within which received sound levels could exceed any 
particular level of concern.
    (2) With a large airgun array, it is unlikely that cetaceans would 
be exposed to airgun pulses at a sufficiently high level for a 
sufficiently long period to cause more than mild TTS, given the 
relative movement of the vessel and the marine mammal. In this project, 
the gun source is much smaller, so the radius of influence and duration 
of exposure to strong pulses is much smaller, especially in deep and 
intermediate-depth water.
    (3) With a large array of airguns, TTS would be most likely in any 
odontocetes that bow-ride or otherwise linger near the airguns. In the 
present project, the

[[Page 17856]]

anticipated 180-dB distance in deep water is 40 m (131 ft), and the 
waterline at the bow of the Roger Revelle will be approximately 97 m 
(318 ft) ahead of the GI gun.
    To avoid injury, NMFS has determined that cetaceans and pinnipeds 
should not be exposed to pulsed underwater noise at received levels 
exceeding, respectively, 180 and 190 dB re 1 microPa (rms). The 
predicted 180- and 190-dB distances for the GI guns operated by SIO are 
40 m (131 ft) and 10 m (33 ft), respectively, in water depths >1000 m 
(3280 ft). [Those distances actually apply to operations with two 45-
in\3\ G guns, and smaller distances would be expected for the two 45-
in\3\ GI guns to be used here.] These sound levels are the received 
levels above which, in the view of a panel of bioacoustics specialists 
convened by NMFS, one cannot be certain that there will be no injurious 
effects, auditory or otherwise, to marine mammals. More recent TTS data 
imply that, at least for dolphins, TTS is unlikely to occur unless the 
dolphins are exposed to airgun pulses notably stronger than 180 dB re 1 
microPa rms. However NMFS utilizes a precautionary approach of 
requiring shut down at received levels above which we cannot be certain 
there will be no injurious effects to the most sensitive species.
    Permanent Threshold Shift (PTS) - When PTS occurs, there is 
physical damage to the sound receptors in the ear. In some cases, there 
can be total or partial deafness, while in other cases, the animal has 
an impaired ability to hear sounds in specific frequency ranges. There 
is no specific evidence that exposure to pulses of airgun sound can 
cause PTS in any marine mammal, even with large arrays of airguns. 
However, given the possibility that mammals close to an airgun array 
might incur TTS, there has been further speculation about the 
possibility that some individuals occurring very close to airguns might 
incur PTS. Single or occasional occurrences of mild TTS are not 
indicative of permanent auditory damage in terrestrial mammals. 
Relationships between TTS and PTS thresholds have not been studied in 
marine mammals, but are assumed to be similar to those in humans and 
other terrestrial mammals. PTS might occur at a received sound level 20 
dB or more above that inducing mild TTS if the animal were exposed to 
the strong sound for an extended period, or to a strong sound with 
rather rapid rise time-see Appendix A (f) of SIO's application.
    It is highly unlikely that marine mammals could receive sounds 
strong enough to cause permanent hearing impairment during a project 
employing two 45-in\3\ GI guns. In the present project, marine mammals 
are unlikely to be exposed to received levels of seismic pulses strong 
enough to cause TTS, as they would probably need to be within a few 
meters of the airguns for that to occur. Given the higher level of 
sound necessary to cause PTS, it is even less likely that PTS could 
occur. In fact, even the levels immediately adjacent to the airguns may 
not be sufficient to induce PTS, especially since a mammal would not be 
exposed to more than one strong pulse unless it swam immediately 
alongside an airgun for a period longer than the inter-pulse interval 
(6-10 s). Baleen whales generally avoid the immediate area around 
operating seismic vessels. The planned monitoring and mitigation 
measures, including visual monitoring, ramp ups, and shut downs of the 
airguns when mammals are seen within the ``safety radii'', will 
minimize the already-minimal probability of exposure of marine mammals 
to sounds strong enough to induce PTS.
    Non-auditory Physiological Effects - Non-auditory physiological 
effects or injuries that theoretically might occur in marine mammals 
exposed to strong underwater sound include stress, neurological 
effects, bubble formation, resonance effects, and other types of organ 
or tissue damage. There is no evidence that any of these effects occur 
in marine mammals exposed to sound from airgun arrays (even large ones) 
and there have been no direct studies of the potential for airgun 
pulses to elicit any of those effects. NMFS does not anticipate that 
marine mammals would experience any of these effects in response to 
being exposed to the airguns in this proposed study, especially 
considering the small size of the airguns. If any such effects do 
occur, they would probably be limited to unusual situations when 
animals might be exposed at close range for unusually long periods.
    Exposure of laboratory animals, wildlife, and humans to strong 
noise often results in significant increases in adrenal activity, 
including cortisol and/or catecholamine release and related measures of 
stress (see Appendix A of SIO's application). However, it is doubtful 
that any single marine mammal would be exposed to strong seismic sounds 
for sufficiently long that significant physiological stress would 
develop. That is especially so in the case of the present project where 
the airguns are small, the ship's speed is relatively fast (5-8 knots 
or 9.3-14.8 km/h), and each survey does not encompass a large area.
    Gas-filled structures in marine animals have an inherent 
fundamental resonance frequency. If stimulated at that frequency, the 
ensuing resonance could cause damage to the animal. A workshop (Gentry 
[ed.] 2002) was held to discuss whether the stranding of beaked whales 
in the Bahamas in 2000 (Balcomb and Claridge, 2001; NOAA and USN, 2001) 
might have been related to air cavity resonance or bubble formation in 
tissues caused by exposure to noise from naval sonar. A panel of 
experts concluded that resonance in air-filled structures was not 
likely to have caused this stranding. Opinions were less conclusive 
about the possible role of gas (nitrogen) bubble formation/growth in 
the Bahamas stranding of beaked whales.
    Until recently, it was assumed that diving marine mammals are not 
subject to the bends or air embolism. However, a short paper concerning 
beaked whales stranded in the Canary Islands in 2002 suggests that 
cetaceans might be subject to decompression injury in some situations 
(Jepson et al., 2003). If so, that might occur if they ascend quickly 
when exposed to aversive sounds. However, the interpretation that the 
effect was related to decompression injury is unproven (Piantadosi and 
Thalmann 2004; Fernandez et al., 2004). Even if that effect can occur 
during exposure to mid-frequency sonar, there is no evidence that this 
type of effect occurs in response to airgun sounds. It is especially 
unlikely in the case of the proposed survey, involving only two GI 
guns.
    In general, little is known about the potential for seismic survey 
sounds to cause auditory impairment or other physical effects in marine 
mammals. Available data suggest that such effects, if they occur at 
all, would be limited to short distances and probably to projects 
involving large arrays of airguns. However, the available data do not 
allow for meaningful quantitative predictions of the numbers (if any) 
of marine mammals that might be affected in those ways. Marine mammals 
that show behavioral avoidance of seismic vessels, including most 
baleen whales, some odontocetes, and some pinnipeds, are especially 
unlikely to incur auditory impairment or other physical effects. Also, 
the planned mitigation measures, including ramp ups and shut downs, 
will reduce any such effects that might otherwise occur.
Strandings and Mortality
    Marine mammals close to underwater detonations of high explosives 
can be killed or severely injured, and their auditory organs are 
especially

[[Page 17857]]

susceptible to injury (Ketten et al., 1993; Ketten 1995). Airgun pulses 
are less energetic and have slower rise times, and there is no proof 
that they can cause serious injury, death, or stranding even in the 
case of large airgun arrays. However, the association of several 
strandings of beaked whales with naval exercises and, in one case, an 
L-DEO seismic survey, has raised the possibility that beaked whales 
exposed to strong pulsed sounds may be especially susceptible to injury 
and/or behavioral reactions that can lead to stranding. Appendix A (g) 
of SIO's application provides additional details.
    Seismic pulses and mid-frequency sonar pulses are quite different. 
Sounds produced by airgun arrays are broadband with most of the energy 
below 1 kHz. Typical military mid-frequency sonars operate at 
frequencies of 2-10 kHz, generally with a relatively narrow bandwidth 
at any one time. Thus, it is not appropriate to assume that there is a 
direct connection between the effects of military sonar and seismic 
surveys on marine mammals. However, evidence that sonar pulses can, in 
special circumstances, lead to physical damage and mortality (NOAA and 
USN 2001; Jepson et al., 2003), even if only indirectly, suggests that 
caution is warranted when dealing with exposure of marine mammals to 
any high-intensity pulsed sound.
    In May 1996, 12 Cuvier's beaked whales stranded along the coasts of 
Kyparissiakos Gulf in the Mediterranean Sea. That stranding was 
subsequently linked to the use of low- and medium-frequency active 
sonar by a North Atlantic Treaty Organization (NATO) research vessel in 
the region (Frantzis 1998). In March 2000, a population of Cuvier's 
beaked whales being studied in the Bahamas disappeared after a U.S. 
Navy task force using mid-frequency tactical sonars passed through the 
area; some beaked whales stranded (Balcomb and Claridge, 2001; NOAA and 
USN, 2001).
    In September 2002, a total of 14 beaked whales of various species 
stranded coincident with naval exercises in the Canary Islands (Martel 
n.d.; Jepson et al., 2003; Fernandez et al., 2003). Also in Sept. 2002, 
there was a stranding of two Cuvier's beaked whales in the Gulf of 
California, Mexico, when the L-DEO vessel Maurice Ewing was operating a 
20-gun, 8490-in\3\ array in the general area. The link between the 
stranding and the seismic surveys was inconclusive and not based on any 
physical evidence (Hogarth, 2002; Yoder, 2002). Nonetheless, that plus 
the incidents involving beaked whale strandings near naval exercises 
suggests a need for caution in conducting seismic surveys in areas 
occupied by beaked whales.
    The present project will involve a much smaller sound source than 
used in typical seismic surveys. That, along with the monitoring and 
mitigation measures that are planned, are expected to minimize any 
possibility for strandings and mortality.

Potential Effects of Other Acoustic Devices

Bathymetric Sonar Signals
    A multi-beam bathymetric sonar (Simrad EM120, 11.25-12.6 kHz) will 
be operated from the source vessel during much of the planned study. 
Sounds from the multi-beam sonar are very short pulses. Most of the 
energy in the sound pulses emitted by the multi-beam is at moderately 
high frequencies, centered at 12 kHz. The beam is narrow (1[deg] or 
2[deg]) in fore-aft extent, and wide (150[deg]) in the cross-track 
extent. Each ping consists of nine successive transmissions (segments) 
at different cross-track angles. Any given mammal at depth near the 
track line would be in the main beam for only a fraction of a second.
    Tactical Navy sonars that have been linked to avoidance reactions 
and stranding of cetaceans (1) generally are more powerful than the 
Simrad EM120, (2) have a longer pulse duration, and (3) are directed 
close to omnidirectionally, vs. downward for the Simrad EM120. The area 
of possible influence of the Simrad EM120 is a much smaller narrow band 
oriented in the cross-track direction below the source vessel. Marine 
mammals that encounter the Simrad EM120 at close range are unlikely to 
be subjected to repeated pulses because of the narrow fore-aft width of 
the beam, and will receive only limited amounts of pulse energy because 
of the short pulses. In assessing the possible impacts of the 15.5 kHz 
Atlas Hydrosweep (a similar model), Boebel et al. (2004) noted that the 
critical sound pressure level at which TTS may occur is 203.2 dB re 1 
microPa (rms). The critical region included an area of 43 m (141 ft) in 
depth, 46 m (151 ft) wide athwartship, and 1 m (3.3 ft) fore-and-aft 
(Boebel et al., 2004).
    Behavioral reactions of free-ranging marine mammals to military and 
other sonars appear to vary by species and circumstance. Observed 
reactions have included silencing and dispersal by sperm whales 
(Watkins et al., 1985), increased vocalizations and no dispersal by 
pilot whales (Rendell and Gordon, 1999), and the previously-mentioned 
beachings by beaked whales. However, all of those observations are of 
limited relevance to the present situation. Pulse durations from those 
sonars were much longer than those of the SIO multi-beam sonar, and a 
given mammal would have received many pulses from the naval sonars. 
During SIO's operations, the individual pulses will be very short, and 
a given mammal would not receive many of the downward-directed pulses 
as the vessel passes by.
    Captive bottlenose dolphins and a white whale exhibited changes in 
behavior when exposed to 1 s pulsed sounds at frequencies similar to 
those that will be emitted by the multi-beam sonar used by SIO, and to 
shorter broadband pulsed signals. Behavioral changes typically involved 
what appeared to be deliberate attempts to avoid the sound exposure 
(Schlundt et al., 2000; Finneran et al., 2002). The relevance of those 
data to free-ranging odontocetes is uncertain, and in any case, the 
test sounds were quite different in either duration or bandwidth as 
compared with those from a bathymetric sonar.
    Because of the shape of the beam, NMFS believes it unlikely that 
marine mammals will be exposed to the bathymetric sonar at levels at or 
above those likely to cause harassment. Further, NMFS believes that the 
brief exposure of cetaceans or pinnipeds to one pulse, or small numbers 
of signals, from the multi-beam bathymetric sonar system are not likely 
to result in the harassment of marine mammals.
Sub-bottom Profiler Signals
    A sub-bottom profiler will be operated from the source vessel at 
all times during the planned study. Sounds from the sub-bottom profiler 
are very short pulses, occurring for 12 or 24 ms once every 4.5-8 
seconds. Most of the energy in the sound pulses emitted by this sub-
bottom profiler is at mid frequencies, centered at 3.5 kHz. The beam 
width is approximately 80o (cone-shaped) and is directed downward.
    The sub-bottom profiler on the Roger Revelle has a stated maximum 
source level of 211 dB re 1 microPa m (see section I of SIO's 
application). Thus, the received level would be expected to decrease to 
180 dB and 160 dB approximately 35 m and 350 m below the transducer, 
respectively, assuming spherical spreading. Corresponding distances in 
the horizontal plane would be substantially lower, given the 
directionality of this source.
    Marine mammal behavioral reactions to other pulsed sound sources 
are discussed above, and responses to the sub-bottom profiler are 
likely to be similar to those for other pulsed sources

[[Page 17858]]

if received at the same levels. However, the pulsed signals from the 
sub-bottom profiler are weaker than those from both the multi-beam 
sonar and the two GI guns. Behavioral responses are not expected unless 
marine mammals are very close to the source, e.g., within approximately 
350 m below the vessel, or a lesser distance to the side. It is 
unlikely that the sub-bottom profiler produces pulse levels strong 
enough to cause hearing impairment or other physical injuries even in 
an animal that is (briefly) in a position near the source.
    The sub-bottom profiler is usually operated simultaneously with 
other higher-power acoustic sources. Many marine mammals will move away 
in response to the approaching higher-power sources or the vessel 
itself before the mammals would be close enough for there to be any 
possibility of effects from the less intense sounds from the sub-bottom 
profiler. In the case of mammals that do not avoid the approaching 
vessel and its various sound sources, mitigation measures that would be 
applied to minimize effects of the higher-power sources would further 
reduce or eliminate any minor effects of the sub-bottom profiler.
    Because of the shape of the conical beam and the power of the 
source, NMFS believes it unlikely that marine mammals will be exposed 
to the bathymetric sonar at levels at or above those likely to cause 
harassment. Further, NMFS believes that the brief exposure of cetaceans 
or pinnipeds to small numbers of signals from the multi-beam 
bathymetric sonar system are not likely to result in the harassment of 
marine mammals.

Estimated Take by Incidental Harassment

    All anticipated takes would be ``takes by harassment'', involving 
temporary changes in behavior. The proposed mitigation measures are 
expected to minimize the possibility of injurious takes. (However, as 
noted earlier, there is no specific information demonstrating that 
injurious ``takes'' would occur even in the absence of the planned 
mitigation measures.) In the sections below, we describe methods to 
estimate ``take by harassment'', and present estimates of the numbers 
of marine mammals that might be affected during the proposed seismic 
survey in the northeast Indian Ocean. The estimates are based on the 
best available data concerning marine mammal densities (numbers per 
unit area) and estimates of the size of the area where effects 
potentially could occur.
    Because there is very little information on marine mammal densities 
in the proposed survey area, densities were used from two of 
Longhurst's (2007) biogeographic provinces in the ETP that are 
oceanographically similar to the two provinces in which the seismic 
activities will take place (see further, below).
    SIO's application presents two types of estimates: estimates of the 
number of potential ``exposures'', and estimates of the number of 
different individual marine mammals that might potentially be exposed 
to sound levels [gteqt]160 dB re 1 microPa (rms). The distinction 
between ``exposures'' and ``number of different individuals exposed'' 
is marginally relevant in this project, because the plan does not call 
for repeated GI gun operations through the same or adjacent waters, and 
the 2 GI guns that will be used ensonify a relatively small area. 
Estimates of the number of exposures are considered precautionary 
overestimates of the actual numbers of different individuals 
potentially exposed to seismic sounds, because in all likelihood, 
exposures represent repeated exposures of some of the same individuals 
as discussed in the sections that follow. Because of their 
precautionary nature, the fact that they are the numbers SIO requested 
authorization for, and the fact that they differ only slightly from the 
estimated number of individuals, NMFS will use the estimated number of 
exposures for the take estimate.
    The following estimates are based on a consideration of the number 
of marine mammals that might be disturbed appreciably by operations 
with the 2 GI guns to be used during approximately 2700 line-km of 
surveys at five sites on the Ninety East Ridge in the northeastern 
Indian Ocean. The anticipated radii of influence of the multi-beam 
sonar and sub-bottom profiler are less than those for the GI guns. It 
is assumed that, during simultaneous operations of the multi-beam sonar 
and airguns, any marine mammals close enough to be affected by the 
sonar would already be affected by the airguns. No animals are expected 
to exhibit more than short-term and inconsequential responses to the 
multi-beam sonar and sub-bottom profiler, given their characteristics 
(e.g., narrow downward-directed beam) and other considerations 
described previously. Therefore, no additional allowance is included 
for animals that might be affected by those sources. Any effects of the 
multi-beam sonar and sub-bottom profiler during times when they are 
operating but the airguns are silent are not considered.
    Few systematic aircraft- or ship-based surveys have been conducted 
for marine mammals in offshore waters of the Indian Ocean, and the 
species of marine mammals that occur there are not well known. The 
density estimates used in this assessment are from two sources, as 
noted above. The most comprehensive and recent density data available 
for cetaceans of the ETP are from 1986 1996 NMFS ship surveys reported 
by Ferguson and Barlow (2001).
    (1) Some of those waters are in Longhurst's (2007) Pacific 
Equatorial Divergence Province (PEQD), which is similar to the Indian 
Monsoon Gyres Province (MONS), in which 3 of the 5 proposed seismic 
surveys in the northeastern Indian Ocean will occur. The similarities 
are that they are both high-nitrate, low-chlorophyll regions of the 
oceans that support relatively large populations of yellowfin, bigeye, 
and skipjack tuna. SIO used the 1986 1996 data from blocks 162-170, 
202-209, and 213-216 of Ferguson and Barlow (2001) for the species 
group density estimates given in Table 3 of SIO's application (and used 
to calculate the take estimates in Table 1 here).
    (2) Some of the surveys conducted by Ferguson and Barlow (2001) in 
the ETP are in Longhurst's (2007) North Pacific Tropical Gyre Province 
(NPTG), which is similar to the Indian South Subtropical Gyre Province 
(ISSG), in which 2 of the 5 proposed seismic surveys will occur. The 
similarities are that they are both low-nitrate, low-chlorophyll 
regions of the oceans that support relatively large bigeye and 
yellowfin tuna populations. SIO used the 1986 1996 data from blocks 
105, 106, 111, 112, and 125 131 of Ferguson and Barlow (2001) to 
compute the species group densities in Table 4 of their application 
(and used to calculate the take estimates in Table 1 here).
    The species that will be encountered during the Indian Ocean survey 
will be different than those sighted during the surveys in the ETP. 
However, the overall abundance of species groups with generally similar 
habitat requirements are expected to be roughly similar. No density 
data were available for any cetacean species in the proposed seismic 
survey area. Thus, data from offshore areas of the ETP to estimate the 
densities of beaked whales, delphinids, small whales, and mysticetes in 
the northeastern Indian Ocean were used. SIO then estimated the 
relative abundance of individual species within the species groups on a 
scale of 1 (rare) to 10 (abundant) using various surveys and other 
information from areas near the study area, and general information on 
species such as latitudinal ranges,

[[Page 17859]]

water depth preferences, and group sizes (see Column 1 in Tables 3 and 
4 of SIO's application). Finally, SIO estimated the density of each 
species expected to occur in the survey area from the densities for 
species groups in Tables 3 and 4 of their application by multiplying 
their relative abundance/the relative abundance for all species in the 
species group times the density for the species group.
    Tables 3 and 4 in SIO's application give the average and maximum 
densities for each species group of marine mammals reported in the PEQD 
and NPTG provinces of the ETP, corrected for effort, based on the 
densities reported in Ferguson and Barlow (2001). The densities from 
those studies had been corrected, by the original authors, for both 
detectability bias and availability bias. Detectability bias is 
associated with diminishing sightability with increasing lateral 
distance from the track line [f(0)]. Availability bias refers to the 
fact that there is less-than 100 percent probability of sighting an 
animal that is present along the survey track line, and it is measured 
by g(0).
    It should be noted that the following estimates of ``takes by 
harassment'' assume that the seismic surveys will be undertaken and 
completed; in fact, the planned number of line-kms has been increased 
by 25 percent to accommodate lines that may need to be repeated, 
equipment testing, etc. As is typical on offshore ship surveys, 
inclement weather, equipment malfunctions, and other survey priorities 
(rock dredging, magnetic surveys) may cause delays and may limit the 
number of useful line-kms of seismic operations that can be undertaken. 
Furthermore, any marine mammal sightings within or near the designated 
safety zones will result in the shut down of seismic operations as a 
mitigation measure. Thus, the following estimates of the numbers of 
marine mammals potentially exposed to 160-dB sounds are precautionary, 
and probably overestimate the actual numbers of marine mammals that 
might be involved. The estimates assume that there are no conflicts in 
survey priorities or weather, equipment, or mitigation delays, which is 
unlikely, particularly given the complexity of the tasks and equipment 
involved.
    There is some uncertainty about the representativeness of the data 
and the assumptions used in the take calculations. However, the 
approach used here is believed to be the best available approach. Also, 
to provide some allowance for the uncertainties, ``maximum estimates'' 
as well as ``best estimates'' of the numbers potentially affected have 
been derived. Best and maximum estimates are based on the average and 
maximum estimates of densities reported in the selected datasets that 
were used from Ferguson and Barlow (2001) described above. SIO has 
requested authorization for the take of the maximum estimates and NMFS 
has analyzed the maximum estimate for it's effect on the species or 
stock.
    The potential number of occasions when members of each species 
might be exposed to received levels [gteqt]160 dB re 1 microPa (rms) 
was calculated by multiplying
    <bullet> Its expected density, either ``average'' (i.e., best) or 
``maximum'', corrected as described above, times
    <bullet> The anticipated total line-kilometers of operations with 
the 2 GI guns (including turns and additional buffer line km to allow 
for repeating of lines due to equipment malfunction, bad weather, 
etc.), times
    <bullet> The cross-track distances within which received sound 
levels are predicted to be [gteqt]160 dB.
    For the 2 GI guns, that cross track distance is 2x the predicted 
160-dB radii of 400 m (1312 ft) in water depths >1000 m (3280 ft).
    Based on that method, the ``best'' and ``maximum'' estimates of the 
number of marine mammal exposures to airgun sounds [gteqt]160 dB re 1 
microPa (rms) were obtained for each of the ecological provinces using 
the reported average and maximum densities from Tables 3 and 4 of SIO's 
application. The two estimates were then added to give totals. Of the 
five endangered cetacean species that could be present, the best and 
maximum estimates show that only one blue whale and one sperm whale may 
be exposed to such noise levels (Table 5 of SIO's application). The 
vast majority of the best and maximum exposures to seismic sounds 
[gteqt]160 dB would involve delphinids. Maximum estimates of exposures 
for the species with the highest numbers are, in descending order, 
spinner dolphin (215 exposures), common and Risso's dolphins (151 
exposures), and bottlenose dolphin (129 exposures). Estimates for other 
species are lower (Table 1).
    The far right column in Table 1, ``Requested Take Authorization'', 
shows the numbers for which ``take authorization'' is requested. The 
requested take authorization numbers are calculated as indicated above 
based on the maximum densities reported by Ferguson and Barlow (2001) 
in any of the survey blocks included in the average density estimates. 
For those species for which very low numbers to none are estimated to 
be exposed to seismic sounds [gteqt]160 dB, SIO included allowance for 
encountering one group based on the mean group size. Where group sizes 
are less than five, SIO assigned a group size of five. However, for 
endangered species, NMFS only plans to authorize take for one sperm 
whale and one blue whale.
    The best and maximum estimates are based on 160-dB distances 
predicted from the acoustic model applied by L-DEO. Based on the 
empirical calibration data collected in the Gulf of Mexico in 2003 for 
L-DEO's 2 GI guns in deep water (510 m (1673 ft)), actual 160-dB 
distances in deep water are likely to be less than predicted (Tolstoy 
et al., 2004). Additionally, the requested take is based on maximum 
exposure estimates (based on maximum density estimates). Given these 
considerations, the predicted numbers of marine mammals that might be 
exposed to sounds [gteqt]160 dB may be somewhat overestimated.
    The stock structures of the marine mammals present in the Indian 
Ocean have not been identified by NMFS; therefore, NMFS must make the 
necessary findings based on the species as a whole. The species 
anticipated to be affected during the proposed activities are wide-
ranging species. Though worldwide abundance (or abundance outside of 
that estimated for the U.S. stocks) has not been estimated, localized 
surveys in the west tropical Indian Ocean and elsewhere have been 
conducted. Since the take estimates proposed in this document fall 
largely within 6 percent (all but common dolphin (21 percent) and 
rough-toothed dolphin (14 percent)) of the numbers estimated to be 
present during a localized survey of the west tropical Indian Ocean, 
and the species range far beyond the Indian Ocean (i.e., the abundance 
of the species is notably larger), NMFS believes that the estimated 
take numbers for these are small relative both to the worldwide 
abundance of these species and to numbers taken in other activities 
that have been authorized for incidental take of these species.

Potential Effects on Habitat

    The proposed airgun operations will not result in any permanent 
impact on habitats used by marine mammals, or to the food sources they 
use. The main impact issue associated with the proposed activities will 
be temporarily elevated noise levels and the associated direct effects 
on marine mammals, as discussed above.
    One of the reasons for the adoption of airguns as the standard 
energy source for marine seismic surveys was that they (unlike the 
explosives used in the distant past) do not result in any

[[Page 17860]]

appreciable fish kill. However, the existing body of information 
relating to the impacts of seismic on marine fish and invertebrate 
species is very limited. The various types of potential effects of 
exposure to seismic on fish and invertebrates can be considered in 
three categories: (1) pathological, (2) physiological, and (3) 
behavioral. Pathological effects include lethal and sub-lethal damage 
to the animals, physiological effects include temporary primary and 
secondary stress responses, and behavioral effects refer to changes in 
exhibited behavior of the fish and invertebrates. The three categories 
are interrelated in complex ways. For example, it is possible that 
certain physiological and behavioral changes could potentially lead to 
the ultimate pathological effect on individual animals (i.e., 
mortality).
    The available information on the impacts of seismic surveys on 
marine fish and invertebrates provides limited insight on the effects 
only at the individual level. Ultimately, the most important knowledge 
in this area relates to how significantly seismic affects animal 
populations.
    The following sections provide an overview of the information that 
exists on the effects of seismic surveys on fish and invertebrates. The 
information comprises results from scientific studies of varying 
degrees of soundness and some anecdotal information.
    Pathological Effects - In water, acute injury and death of 
organisms exposed to seismic energy depends primarily on two features 
of the sound source: (1) the received peak pressure, and (2) the time 
required for the pressure to rise and decay (Hubbs and Rechnitzer, 1952 
in Wardle et al., 2001). Generally, the higher the received pressure 
and the less time it takes for the pressure to rise and decay, the 
greater the chance of acute pathological effects. Considering the peak 
pressure and rise/decay time characteristics of seismic airgun arrays 
used today, the pathological zone for fish and invertebrates would be 
expected to be within a few meters of the seismic source (Buchanan et 
al., 2004). For the proposed survey, any injurious effects on fish 
would be limited to very short distances, especially considering the 
small source planned for use in this project (two 45-in\3\ GI guns).
    Matishov (1992) reported that some cod and plaice died within 48 
hours of exposure to seismic pulses 2 m (6.5 ft) from the source. No 
other details were provided by the author. On the other hand, there are 
numerous examples of no fish mortality as a result of exposure to 
seismic sources (Falk and Lawrence 1973; Holliday et al., 1987; La 
Bella et al., 1996; Santulli et al., 1999; McCauley et al., 2000a, 
2000b; Bjarti, 2002; IMG, 2002; McCauley et al., 2003; Hassel et al., 
2003).
    There are examples of damage to fish ear structures from exposure 
to seismic airguns (McCauley et al., 2000a, 2000b, 2003), but it should 
be noted the experimental fish were caged and exposed to high 
cumulative levels of seismic energy. Atlantic salmon were exposed 
within 1.5 m (4.9 ft) of underwater explosions (Sverdrup et al., 1994). 
Compared to airgun sources, explosive detonations are characterized by 
higher peak pressures and more rapid rise and decay times, and are 
considered to have greater potential to damage marine biota. In spite 
of this, no salmon mortality was observed immediately after exposure or 
during the seven-day monitoring period following exposure.
    Some studies have also provided some information on the effects of 
seismic exposure on fish eggs and larvae (Kostyuchenko, 1972; Dalen and 
Knutsen, 1986; Holliday et al., 1987; Matishov, 1992; Booman et al., 
1996; Dalen et al., 1996). Overall, impacts appeared to be minimal and 
any mortality was generally not significantly different from the 
experimental controls. Generally, any observed larval mortality 
occurred after exposures within 0.5 3 m (1.6-9.8 ft) of the airgun 
source. Matishov (1992) did report some retinal tissue damage in cod 
larvae exposed at 1 m (3.3 ft) from the airgun source. Saetre and Ona 
(1996) applied a 'worst-case scenario' mathematical model to 
investigate the effects of seismic energy on fish eggs and larvae, and 
concluded that mortality rates caused by exposure to seismic are so low 
compared to natural mortality that the impact of seismic surveying on 
recruitment to a fish stock must be regarded as insignificant.
    The pathological impacts of seismic energy on marine invertebrate 
species have also been investigated. Christian et al. (2003) exposed 
adult male snow crabs, egg-carrying female snow crabs, and fertilized 
snow crab eggs to energy from seismic airguns. Neither acute nor 
chronic (12 weeks after exposure) mortality was observed for the adult 
male and female crabs. There was a significant difference in 
development rate noted between the exposed and unexposed fertilized 
eggs. The egg mass exposed to seismic energy had a higher proportion of 
less-developed eggs than the unexposed mass. It should be noted that 
both egg masses came from a single female and that any measure of 
natural variability was unattainable. However, a result such as this 
does point to the need for further study.
    Pearson et al. (1994) exposed Stage II larvae of the Dungeness crab 
to single discharges from a seven-airgun seismic array and compared 
their mortality and development rates with those of unexposed larvae. 
For immediate and long-term survival and time to molt, this field 
experiment did not reveal any statistically-significant differences 
between the exposed and unexposed larvae, even those exposed within 1 m 
(3.3 ft) of the seismic source.
    Bivalves of the Adriatic Sea were also exposed to seismic energy 
and subsequently assessed (LaBella et al., 1996). No effects of the 
exposure were noted.
    To date, there have not been any well-documented cases of acute 
post-larval fish or invertebrate mortality as a result of exposure to 
seismic sound under normal seismic operating conditions. Sub-lethal 
injury or damage has been observed, but generally as a result of 
exposure to very high received levels of sound, significantly higher 
than the received levels generated by the single GI gun sound source to 
be used in the proposed study. Acute mortality of eggs and larvae have 
been demonstrated in experimental exposures, but only when the eggs and 
larvae were exposed very close to the seismic sources and the received 
pressure levels were presumably very high. Limited information has not 
indicated any chronic mortality as a direct result of exposure to 
seismic.
    Physiological Effects - Biochemical responses by marine fish and 
invertebrates to acoustic stress have also been studied, although in a 
limited way. Studying the variations in the biochemical parameters 
influenced by acoustic stress might give some indication of the extent 
of the stress and perhaps forecast eventual detrimental effects. Such 
stress could potentially affect animal populations by reducing 
reproductive capacity and adult abundance.
    McCauley et al. (2000a, 2000b) used various physiological measures 
to study the physiological effects of exposure to seismic energy on 
various fish species, squid, and cuttlefish. No significant 
physiological stress increases attributable to seismic energy were 
detected. Sverdrup et al. (1994) found that Atlantic salmon subjected 
to acoustic stress released primary stress hormones, adrenaline and 
cortisol, as a biochemical response although there were different 
patterns of delayed increases for the different indicators. Caged 
European sea bass were exposed to seismic energy and numerous

[[Page 17861]]

biochemical responses were indicated. All returned to their normal 
physiological levels within 72 hours of exposure.
    Stress indicators in the haemolymph of adult male snow crabs were 
monitored after exposure of the animals to seismic energy (Christian et 
al., 2003). No significant differences between exposed and unexposed 
animals were found in the stress indicators (e.g., proteins, enzymes, 
cell type count).
    Primary and secondary stress responses of fish after exposure to 
seismic energy all appear to be temporary in any studies done to date. 
The times necessary for these biochemical changes to return to normal 
are variable depending on numerous aspects of the biology of the 
species and of the sound stimulus.
    Summary of Physical (Pathological and Physiological) Effects - As 
indicated in the preceding general discussion, there is a relative lack 
of knowledge about the potential physical (pathological and 
physiological) effects of seismic energy on marine fish and 
invertebrates. Available data suggest that there may be physical 
impacts on egg, larval, juvenile, and adult stages at very close range. 
Considering typical source levels associated with commercial seismic 
arrays, close proximity to the source would result in exposure to very 
high energy levels. Again, this study will employ a sound source that 
will generate low energy levels. Whereas egg and larval stages are not 
able to escape such exposures, juveniles and adults most likely would 
avoid it. In the case of eggs and larvae, it is likely that the numbers 
adversely affected by such exposure would not be that different from 
those succumbing to natural mortality. Limited data regarding 
physiological impacts on fish and invertebrates indicate that these 
impacts are short term and are most apparent after exposure at close 
range.
    The proposed seismic program for 2007 is predicted to have 
negligible to low physical effects on the various life stages of fish 
and invertebrates for its short duration (approximately 49 hours at 
each of five sites on the Ninety East Ridge) and 2700-km extent. 
Therefore, physical effects of the proposed program on the fish and 
invertebrates would be not significant.
    Fish and Invertebrate Acoustic Detection and Production - Hearing 
in fishes was first demonstrated in the early 1900s through studies 
involving cyprinids (Parker, 1903 and Bigelow, 1904 in Kenyon et al., 
1998). Since that time, numerous methods have been used to test 
auditory sensitivity in fishes, resulting in audiograms of over 50 
species. These data reveal great diversity in fish hearing ability, 
mostly attributable to various peripheral modes of coupling the ear to 
internal structures, including the swim bladder. However, the general 
auditory capabilities of <0.2 percent of fish species are known so far.
    For many years, studies of fish hearing have reported that the 
hearing bandwidth typically extends from below 100 Hz to approximately 
1 kHz in fishes without specializations for sound detection, and up to 
approximately 7 kHz in fish with specializations that enhance bandwidth 
and sensitivity. Recently there have been suggestions that certain 
fishes, including many clupeiforms (herring, shads, anchovies, etc.) 
may be capable of detecting ultrasonic signals with frequencies as high 
as 126 kHz (Dunning et al., 1992; Nestler et al., 1992). Studies on 
Atlantic cod, a non-clupeiform fish, suggested that this species could 
detect ultrasound at almost 40 kHz (Astrup and M hl, 1993).
    Mann et al. (2001) showed that the American shad is capable of 
detecting sounds up to 180 kHz. They also demonstrated that the gulf 
menhaden is also able to detect ultrasound, whereas other species such 
as the bay anchovy, scaled sardine, and Spanish sardine only detect 
sounds with frequencies up to approximately 4 kHz.
    Among fishes, at least two major pathways for sound transmission to 
the ear have been identified. The first and most primitive is the 
conduction of sound directly from the water to tissue and bone. The 
fish's body takes up the sound's acoustic particle motion and 
subsequent hair cell stimulation occurs because of the difference in 
inertia between the hair cells and their overlying otoliths. These 
species are known as 'hearing generalists' (Fay and Popper, 1999). The 
second sound pathway to the ears is indirect. The swim bladder or other 
gas bubble near the ears expands and contracts in volume in response to 
sound pressure fluctuations, and the motion is then transmitted to the 
otoliths. While present in most bony fishes, the swim bladder is absent 
or reduced in many other fish species. Only some species of fish with a 
swim bladder appear to be sound-pressure sensitive via this indirect 
pathway to the ears; they are called 'hearing specialists'. Hearing 
specialists have some sort of connection with the inner ear, either via 
bony structures known as Weberian ossicles, extensions of the swim 
bladder, or a swim bladder more proximate to the inner ear. Hearing 
specialists' sound-pressure sensitivity is high and their upper 
frequency range of detection is extended above those species that hear 
only by the direct pathway. Typically, most fish detect sounds of 
frequencies up to 2,000-Hz but, as indicated, others have detection 
ranges that extend to much higher frequencies.
    Fish also possess lateral lines that detect water movements. The 
essential stimulus for the lateral line consists of differential water 
movement between the body surface and the surrounding water. The 
lateral line is typically used in concert with other sensory 
information, including hearing (Sand, 1981; Coombs and Montgomery, 
1999).
    Elasmobranchs (sharks and skates) lack any known pressure-to-
displacement transducers such as swim bladders. Therefore, they 
presumably must rely on the displacement sensitivity of their 
mechanoreceptive cells. Unlike acoustic pressure, the kinetic stimulus 
is inherently directional but its magnitude rapidly decreases relative 
to the pressure component as it propagates outward from the sound 
source in the near field. It is believed that elasmobranches are most 
sensitive to low frequencies, those <1 kHz (Corwin 1981).
    Because they lack air-filled cavities and are often the same 
density as water, invertebrates detect underwater acoustics differently 
than fish. Rather than being pressure sensitive, invertebrates appear 
to be most sensitive to particle displacement. However, their 
sensitivity to particle displacement and hydrodynamic stimulation seem 
poor compared to fish. Decapods, for example, have an extensive array 
of hair-like receptors both within and upon the body surface that could 
potentially respond to water- or substrate-borne displacements. They 
are also equipped with an abundance of proprioceptive organs that could 
serve secondarily to perceive vibrations. Crustaceans appear to be most 
sensitive to sounds of low frequencies, those <1000 Hz (Budelmann, 
1992; Popper et al., 2001).
    Many fish and invertebrates are also capable of sound production. 
It is believed that these sounds are used for communication in a wide 
range of behavioral and environmental contexts. The behaviors most 
often associated with acoustic communication include territorial 
behavior, mate finding, courtship, and aggression. Sound production 
provides a means of long-distance communication and communication when 
underwater visibility is poor (Zelick et al., 1999).
    Behavioral Effects - Because of the apparent lack of serious 
pathological

[[Page 17862]]

and physiological effects of seismic energy on marine fish and 
invertebrates, most concern now centers on the possible effects of 
exposure to seismic surveys on the distribution, migration patterns, 
and catchability of fish. There is a need for more information on 
exactly what effects such sound sources might have on the detailed 
behavior patterns of fish and invertebrates at different ranges. 
Studies investigating the possible effects of seismic energy on fish 
and invertebrate behavior have been conducted on both uncaged and caged 
animals. Studies of change in catch rate regard potential effects of 
seismic energy on larger spatial and temporal scales than are typical 
for close-range studies that often involve caged animals (Hirst and 
Rodhouse, 2000). Hassel et al. (2003) investigated the behavioral 
effects of seismic pulses on caged sand lance in Norwegian waters. The 
sand lance did exhibit responses to the seismic, including an increase 
in swimming rate, an upwards vertical shift in distribution, and 
startle responses. Normal behaviors were resumed shortly after 
cessation of the seismic source. None of the observed sand lance 
reacted by burying into the sand.
    Engas et al. (1996) assessed the effects of seismic surveying on 
Atlantic cod and haddock behavior using acoustic mapping and commercial 
fishing techniques. Results indicated that fish abundance decreased at 
the seismic survey area, and that the decline in abundance and catch 
rate lessened with distance from the survey area. Fish abundance and 
catch rates had not returned to pre-shooting levels five days after 
cessation of shooting. In other airgun experiments, catch per unit 
effort (CPUE) of demersal fish declined when airgun pulses were 
emitted, particularly in the immediate vicinity of the seismic survey 
(Dalen and Raknes, 1985; Dalen and Knutsen, 1986; L kkeborg, 1991; 
Skalski et al., 1992). Reductions in the catch may have resulted from a 
change in behavior of the fish. The fish schools descended to near the 
bottom when the airgun was firing, and the fish may have changed their 
swimming and schooling behavior. Fish behavior returned to normal 
minutes after the sounds ceased.
    Marine fish inhabiting an inshore reef off the coast of Scotland 
were monitored by telemetry and remote camera before, during, and after 
airgun firing (Wardle et al., 2001). Although some startle responses 
were observed, the seismic gun firing had little overall effect on the 
day-to-day behavior of the resident fish.
    Other species involved in studies that have indicated fish 
behavioral responses to underwater sound include rockfish (Pearson et 
al., 1992), Pacific herring (Schwarz and Greer, 1984), and Atlantic 
herring (Blaxter et al., 1981). The responses observed in these studies 
were relatively temporary. What is not known is the effect of exposure 
to seismic energy on fish and invertebrate behaviors that are 
associated with reproduction and migration.
    Studies on the effects of sound on fish behavior have also been 
conducted using caged or confined fish. Such experiments were conducted 
in Australia using fish, squid, and cuttlefish as subjects (McCauley et 
al. (2000a,b). Common observations of fish behavior included startle 
response, faster swimming, movement to the part of the cage furthest 
from the seismic source (i.e., avoidance), and eventual habituation. 
Fish behavior appeared to return pre-seismic state 15 30 min after 
cessation of seismic shooting. Squid exhibited strong startle responses 
to the onset of proximate airgun firing by releasing ink and/or jetting 
away from the source. The squid consistently made use of the 'sound 
shadow' at the surface, where the sound intensity was less than at 3-m 
(9.8 ft) depth. These Australian experiments provided more evidence 
that fish and invertebrate behavior will be modified at some received 
sound level. Again, the behavioral changes seem to be temporary.
    Christian et al. (2003) conducted an experimental commercial 
fishery for snow crab before and after the area was exposed to seismic 
shooting. Although the resulting data were not conclusive, no drastic 
decrease in catch rate was observed after seismic shooting commenced. 
Another behavioral investigation by Christian et al. (2003) involved 
caging snow crabs, positioning the cage 50 m (164 ft) below a seven-gun 
array, and observing the immediate responses of the crabs to the onset 
of seismic shooting by remote underwater camera. No obvious startle 
behaviors were observed. Anecdotal information from Newfoundland, 
Canada, indicated that snow crab catch rates showed a significant 
reduction immediately following a pass by a seismic survey vessel. 
Other anecdotal information from Newfoundland indicated that a school 
of shrimp showing on a fishing vessel sounder shifted downwards and 
away from a nearby seismic source. Effects were temporary in both the 
snow crab and shrimp anecdotes (Buchanan et al., 2004).
    Summary of Behavioral Effects - As is the case with pathological 
and physiological effects of seismic on fish and invertebrates, 
available information is relatively scant and often contradictory. 
There have been well-documented observations of fish and invertebrates 
exhibiting behaviors that appeared to be responses to exposure to 
seismic energy (i.e., startle response, change in swimming direction 
and speed, and change in vertical distribution), but the ultimate 
importance of those behaviors is unclear. Some studies indicate that 
such behavioral changes are very temporary, whereas others imply that 
fish might not resume pre-seismic behaviors or distributions for a 
number of days. There appears to be a great deal of inter- and intra-
specific variability. In the case of finfish, three general types of 
behavioral responses have been identified: startle, alarm, and 
avoidance. The type of behavioral reaction appears to depend on many 
factors, including the type of behavior being exhibited before 
exposure, and proximity and energy level of sound source.
    During the proposed study, only a small fraction of the available 
habitat would be ensonified at any given time, and fish species would 
return to their pre-disturbance behavior once the seismic activity 
ceased. The proposed seismic program is predicted to have negligible to 
low behavioral effects on the various life stages of the fish and 
invertebrates during its short duration (approximately 49 hours at each 
of 5 sites on the Ninety East Ridge) and 2700-km extent.
    Changes in behavior in fish near the airguns might have short-term 
impacts on the ability of cetaceans to feed near the survey area. 
However, only a small fraction of the available habitat would be 
ensonified at any given time, and fish species would return to their 
pre-disturbance behavior once the seismic activity ceased. Thus, the 
proposed survey would have little impact on the abilities of marine 
mammals to feed in the area where seismic work is planned. Some of the 
fish that do not avoid the approaching airguns (probably a small 
number) may be subject to auditory or other injuries.
    Zooplankters that are very close to the source may react to the 
shock wave. These animals have an exoskeleton and no air sacs. Little 
or no mortality is expected. Many crustaceans can make sounds and some 
crustaceans and other invertebrates have some type of sound receptor. 
However, the reactions of zooplankters to sound are not known. Some 
mysticetes feed on concentrations of zooplankton. A reaction by 
zooplankton to a seismic impulse would only be relevant to whales if it 
caused a concentration of zooplankton to scatter. Pressure changes of 
sufficient magnitude to cause this type of reaction would probably 
occur only very close to

[[Page 17863]]

the source. Impacts on zooplankton behavior are predicted to be 
negligible, and this would translate into negligible impacts on feeding 
mysticetes.
    Because of the reasons noted above and the nature of the proposed 
activities (small airguns and limited duration), the proposed 
operations are not expected to have any habitat-related effects that 
could cause significant or long-term consequences for individual marine 
mammals or their populations or stocks.

Monitoring

    Either dedicated marine mammal observers (MMOs) or other vessel-
based personnel will watch for marine mammals near the seismic source 
vessel during all daytime and nighttime airgun operations. GI airgun 
operations will be suspended when marine mammals are observed within, 
or about to enter, designated safety radii where there is a possibility 
of significant effects on hearing or other physical effects. At least 
one dedicated vessel-based MMO will watch for marine mammals near the 
seismic vessel during daylight periods when shooting is being 
conducted, and two MMOs will watch for marine mammals for at least 30 
min prior to start-up of airgun operations. Observations of marine 
mammals will also be made and recorded during any daytime periods 
without airgun operations. At night, the forward-looking bridge watch 
of the ship's crew will look for marine mammals that the vessel is 
approaching, and execute avoidance maneuvers; the 180dB/190dB safety 
radii around the airguns will be continuously monitored by an aft-
looking member of the scientific party, who will call for shutdown of 
the guns if mammals are observed within the safety radii. Nighttime 
observers will be aided by (aft-directed) ship's lights and night 
vision devices (NVDs).
    Observers will be appointed by SIO with NMFS concurrence. Two 
observers will be on the vessel, and both will have gone through NOAA/
NMFS training for marine mammal observations. Observers will be on duty 
in shifts usually of duration no longer than two hours. Use of two 
simultaneous observers prior to start up will increase the 
detectability of marine mammals present near the source vessel, and 
will allow simultaneous forward and rearward observations. Bridge 
personnel additional to the dedicated marine mammal observers will also 
assist in detecting marine mammals and implementing mitigation 
requirements, and before the start of the seismic survey will be given 
instruction in how to do so.
    The Roger Revelle is a suitable platform for marine mammal 
observations, and has been used for that purpose during the routine 
CalCOFI (California Cooperative Oceanic Fisheries Investigations). 
Observing stations will be at the 02 level, with observers' eyes 
approximately 10.4 m (34 ft) above the waterline: one forward on the 02 
deck commanding a forward-centered, approximately 240[deg] view, and 
one atop the aft hangar, with an aft-centered view that includes the 
60-m radius area around the airguns. The eyes of the bridge watch will 
be at a height of approximately 15 m (49 ft); marine mammal observers 
will repair to the enclosed bridge and adjoining aft steering station 
during any inclement weather (unlikely at this place and season), and 
as necessary to use the 50 X ``big-eye'' binoculars that are mounted 
there.
    Standard equipment for marine mammal observers will be 7 X 50 
reticle binoculars and optical range finders. At night, night vision 
equipment will be available. The observers will be in wireless 
communication with ship's officers on the bridge and scientists in the 
vessel's operations laboratory, so they can advise promptly of the need 
for avoidance maneuvers or airgun power-down or shut-down.
    The vessel-based monitoring will provide data required to estimate 
the numbers of marine mammals exposed to various received sound levels, 
to document any apparent disturbance reactions, and thus to estimate 
the numbers of mammals potentially ``taken'' by harassment. It will 
also provide the information needed in order to shut down the GI 
airguns at times when mammals are present in or near the safety zone. 
When a mammal sighting is made, the following information about the 
sighting will be recorded:
    (1) Species, group size, age/size/sex categories (if determinable), 
behavior when first sighted and after initial sighting, heading (if 
consistent), bearing and distance from seismic vessel, sighting cue, 
apparent reaction to seismic vessel (e.g., none, avoidance, approach, 
paralleling, etc.), and behavioral pace.
    (2) Time, location, heading, speed, activity of the vessel 
(shooting or not), sea state, visibility, cloud cover, and sun glare.
    The data listed under (2) will also be recorded at the start and 
end of each observation watch and during a watch, whenever there is a 
change in one or more of the variables.
    All mammal observations and airgun shutdowns will be recorded in a 
standardized format. Data will be entered into a custom database using 
a notebook computer when observers are off duty. The accuracy of the 
data entry will be verified by computerized data validity checks as the 
data are entered, and by subsequent manual checking of the database. 
Those procedures will allow initial summaries of data to be prepared 
during and shortly after the field program, and will facilitate 
transfer of the data to statistical, graphical, or other programs for 
further processing and archiving.
    Results from the vessel-based observations will provide:
    <bullet> The basis for real-time mitigation (airgun shut down).
    <bullet> Information needed to estimate the number of marine 
mammals potentially taken by harassment, which must be reported to 
NMFS.
    <bullet> Data on the occurrence, distribution, and activities of 
marine mammals in the area where the seismic study is conducted.
    <bullet> Information to compare the distance and distribution of 
marine mammals relative to the source vessel at times with and without 
seismic activity.
    <bullet> Data on the behavior and movement patterns of marine 
mammals seen at times with and without seismic activity.

Mitigation

    For the proposed seismic surveys in the Northeastern Indian Ocean 
during May August 2007, SIO will deploy two GI airguns as an energy 
source, with a total discharge volume of 90 in3. The energy from the 
airguns will be directed mostly downward. The small size of the airguns 
to be used during the proposed study will reduce the potential for 
effects relative to those that might occur with a large airgun arrays.
    In addition to marine mammal monitoring, the following mitigation 
measures will be adopted during the proposed seismic program, provided 
that doing so will not compromise operational safety requirements. 
Although power-down procedures are often standard operating practice 
for seismic surveys, it will not be used here because powering down 
from two guns to one gun would make only a small difference in the 180- 
or 190-dB radius - probably not enough to allow continued one-gun 
operations if a mammal came within the safety radius for two guns. 
Mitigation measures that will be adopted are:
    (1) Speed or course alteration;
    (2) Ramp-up and shut-down procedures; and
    (3) Night operations;
    Speed or Course Alteration - If a marine mammal is detected outside 
the

[[Page 17864]]

safety radius and, based on its position and the relative motion, is 
likely to enter the safety radius, the vessel's speed and/or direct 
course may, when practical and safe, be changed in a manner that also 
minimizes the effect to the planned science objectives. The marine 
mammal activities and movements relative to the seismic vessel will be 
closely monitored to ensure that the animal does not approach within 
the safety radius. If the animal appears likely to enter the safety 
radius, further mitigative actions will be taken, i.e. either further 
course alterations or shut down of the airguns.
    Shut-down Procedures - If a marine mammal is detected outside the 
safety radius but is likely to enter the safety radius, and if the 
vessel's course and/or speed cannot be changed to avoid having the 
animal enter the safety radius, the airguns will be shut down before 
the animal is within the safety radius (10 m (33 ft) for pinnipeds 
(190-dB isopleth) or 40 m (131 ft) for cetaceans (180-dB isopleth)). 
Likewise, if a marine mammal is already within the safety radius when 
first detected, the airguns will be shut down immediately.
    Airgun activity will not resume until the animal has cleared the 
safety radius. The animal will be considered to have cleared the safety 
radius if it is visually observed to have left the safety radius, or if 
it has not been seen within the radius for 15 min (small odontocetes 
and pinnipeds) or 30 min (mysticetes and large odontocetes, including 
sperm, pygmy sperm, dwarf sperm, beaked, and bottlenose whales).
    Ramp-up Procedures - A ``ramp-up'' procedure will be followed when 
the airguns begin operating after a period without airgun operations. 
The two GI guns will be added in sequence 5 minutes apart. During ramp-
up procedures, the safety radius for the two GI guns will be 
maintained.
    Night Operations - At night, vessel lights and/or night vision 
devices (NVDs) could be useful in sighting some marine mammals at the 
surface within a short distance from the ship (within the safety radii 
for the two GI guns in deep water). Start up of the airguns will only 
occur in situations when the entire safety radius is visible with 
vessel lights and NVDs.

Reporting

    A report will be submitted to NMFS within 90 days after the end of 
the cruise. The end of the northeastern Indian Ocean cruise is 
predicted to occur between July 16 and August 13, 2007. The report will 
describe the operations that were conducted and the marine mammals that 
were detected near the operations. The report will be submitted to 
NMFS, providing full documentation of methods, results, and 
interpretation pertaining to all monitoring. The 90-day report will 
summarize the dates and locations of seismic operations, marine mammal 
sightings (dates, times, locations, activities, associated seismic 
survey activities), and estimates of the amount and nature of potential 
``take'' of marine mammals by harassment or in other ways.

Endangered Species Act

    Under section 7 of the Endangered Species Act (ESA) the NSF has 
begun consultation on this proposed seismic survey. NMFS will also 
consult on the issuance of an IHA under section 101(a)(5)(D) of the 
MMPA for this activity. Consultation will be concluded prior to a 
determination on the issuance of the IHA.

National Environmental Policy Act (NEPA)

    NSF prepared an Environmental Assessment of a Planned Low-Energy 
Marine Seismic Survey by the Scripps Institution of Oceanography in the 
Northeast Indian Ocean, May July 2007. NMFS will either adopt NSF's EA 
or conduct a separate NEPA analysis, as necessary, prior to making a 
determination on the issuance of the IHA.

Preliminary Determinations

    NMFS has preliminarily determined that the impact of conducting the 
seismic survey in the northeast Indian Ocean may result, at worst, in a 
temporary modification in behavior (Level B Harassment) of small 
numbers of 29 species of cetaceans. Further, this activity is expected 
to result in a negligible impact on the affected species or stocks. The 
provision requiring that the activity not have an unmitigable adverse 
impact on the availability of the affected species or stock for 
subsistence uses does not apply for this proposed action.
     For reasons stated peviously in this document, this determination 
is supported by: (1) the likelihood that, given sufficient notice 
through relatively slow ship speed and rampup, marine mammals are 
expected to move away from a noise source that is annoying prior to its 
becoming potentially injurious; (2) the fact that marine mammals would 
have to be closer than 40 m from the vessel to be exposed to levels of 
sound (180 dB) believed to have even a minimal chance of causing TTS; 
and (3) the likelihood that marine mammal detection ability by trained 
observers is high at that short distance from the vessel. As a result, 
no take by injury or death is anticipated and the potential for 
temporary or permanent hearing impairment is very low and will be 
avoided through the incorporation of the proposed mitigation measures.
    While the number of potential incidental harassment takes will 
depend on the distribution and abundance of marine mammals in the 
vicinity of the survey activity, the number of potential harassment 
takings is estimated to be small, less than a few percent of any of the 
estimated population sizes, and has been mitigated to the lowest level 
practicable through incorporation of the measures mentioned previously 
in this document.

Proposed Authorization

    As a result of these preliminary determinations, NMFS proposes to 
issue an IHA to SIO for conducting a low-energy seismic survey in the 
Indian Ocean from May - August, 2007, provided the previously mentioned 
mitigation, monitoring, and reporting requirements are incorporated.

    Dated: April 4, 2007.
David Cottingham,
Acting Deputy Director, Office of Protected Resources, National Marine 
Fisheries Service.
[FR Doc. E7-6750 Filed 4-9-07; 8:45 am]
BILLING CODE 3510-22-S


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